1. Field of the Invention
This invention relates to tube bending and, more particularly, to a tool for strategically cutting out a portion of the tubing to facilitate bending thereof and a method of bending tubing utilizing the novel cutting tool.
2. Background Art
There are a number of different techniques used to bend hollow tubing made from iron, steel, lead, aluminum and the like. For example, conventional brakes, such as commonly used to bend sheet metal, are also utilized to bend tubing. The tubing is forcibly urged against a curved surface on a die receptacle matched to the cross section of the tubing. U-shaped, V-shaped, circular cross sections, and the like, can be readily accommodated by correspondingly formed dies. While this is the most commonly employed method for bending tubing, it has a number of drawbacks.
It is difficult with a conventional brake to consistently and accurately bend tubing. Another drawback with the conventional brake is that the bends cannot be made with sharp, squared corners. For example, if a large diameter tube is bent at 90.degree., the corner is accurately formed. A further drawback with the conventional brake is that it is generally unsuitable for bending tubing having a square/rectangular cross section. When one attempts to bend square material with a brake, the tubing side walls tend to collapse and the corners bulge, thereby producing an unsightly product.
As an alternative to the use of a brake, a core die may be inserted into the tubing to cooperate with another die through which the tubing is cut, after which bending can proceed. Bending by this method is time consuming, complicated and requires the stocking of separate core dies to match individual tubing cross sections. Further, the internal cross section of tubing is generally inconsistent due to welds, burrs, and the like projecting into the tubing hollow.
As an alternative to bending tubing, it is known to cut the tubing into separate parts and join the parts at desired angles, as by welding This technique also has several drawbacks. The pieces must be held in proper relationship, as by a jig, and thereafter welded in several spots. Inevitably, inconsistent and inaccurate assembly results. Further, welding leaves an exposed, unsightly bead at the point of connection. Overall, such a technique is time consuming, complicated and thereby expensive.
In addition to the fact that the above bending techniques are relatively complicated to perform and time consuming, the finished product produced by the above techniques may be aesthetically unpleasing. The integrity, as well as the appearance, of the finished product, may vary from one assembly to the next. These problems are particularly prevalent with square tubing.
The inventor herein previously developed a bending technique that is an alternative to the above described techniques and which has particular utility in overcoming the problems associated with bending square tubing. According to that invention, a cutting blade is directed through a square tubing piece so as to cut a V-shaped notch through the walls of one facing wall pair and a square/rectangular notch in a third wall between the walls of the one wall pair and connecting the spaced, V-shaped notches. The cutting blade scores the wall opposite the third wall to define a weakening fold line The wall opposite the third wall can thus be folded to bring the edges of the tubing parts bounding the V-shaped notches into close proximity. The parts can be spot welded to maintain the desired configuration of the tubing.
The cutting blade used to form the notches in the tubing has heretofore been made with wavy, shearing edges. While these cutting blades have been very effective in operation, they are relatively complicated, and thus expensive, to manufacture. Further, there are several sharp points on the wavy edge which are prone to chipping. A chip anywhere on the blade may render the entire blade useless. Therefore, constant inspection of the blade by the press operator is required resulting in significant down time.